The present invention relates to semiconductor structures, and more particularly to altering the orientation of grain boundaries of certain semiconductor layers.
One particularly useful device in the semiconductor industry, and particularly in the analog radio frequency (RF) device industry, is the epitaxial-base bipolar transistor. In certain configurations, the epitaxial-base bipolar transistor comprises a base portion which includes an epitaxial portion adjacent a polycrystalline portion. A crystal "grain boundary" exists at the interface between the polycrystalline portion and the epitaxial portion of the base. The grain boundary has a particular orientation. The nature of this orientation significantly affects the base resistance (R.sub.b) of the device. It is well understood by those skilled in the art that the base resistance effects important performance parameters such as power gain and noise figure, in the case of RF devices. It is desirable to minimize R.sub.b.
Consequently, what is needed is a method for affecting/altering the orientation of a grain boundary in a semiconductor layer, and in particular the orientation of a grain boundary in the base of an epitaxial-base bipolar transistor, in order to favorably affect R.sub.b.